As is well known in the art, a Clos switching network is a network of switches that is architected in a multi-stage configuration so that fewer switching points are necessary to implement connections between its inputs and outputs than would be required by a single stage switch architecture having the same input and output structure. In the prior art, three-stage Clos switching networks have been typically prevented from providing point-to-multipoint broadcasting. This is because it was known that to allow such broadcasting would tend to introduce the blocking of attempts to later establish point-to-point connections, unless the network were continually rearranged. However, the effort and time required to continually rearrange such a network, in order to maintain its nonblocking characteristics, when providing point-to-multipoint broadcasting, were perceived to be prohibitive.
And indeed, the maintenance of such nonblocking characteristics is often regarded as very important. For example, it is especially important for Clos switching networks that are to assist in providing alternate paths for use in the rerouting of signals which are carried over transport paths that become disturbed. Such alternate paths are carried through the Clos switching network via point-to-point connections and it must be ensured, for well known reasons in the switching art, that only a short time be taken to establish these alternate paths. To ensure that the time taken to establish the alternate paths is short, it is necessary that each one of the point-to-point connections, which must be established through the Clos switching network to support the alternate paths, be immediately available. Such immediate availability can only be achieved if the point-to-point nonblocking characteristics of the Clos switching network are maintained. However, as noted above, the maintenance of such nonblocking characteristics was perceived to limit the ability of the Clos switching network to be reconfigured, and hence, to limit its ability to support point-to-multipoint broadcasting.